Collectors can protect themselves well enough with a few basic safeguards - I'd like to share the thought process I go through when buying on eBay. This is a note for beginner to average collectors; those with more experience can skip it (or add your comments!).

1. Avoid private auctions, low-feedback sellers, and anything with a blurred picture, unless you already know and trust the seller. Buy with preference from dealers with established web-sites and/or bricks
and mortar presence.

(b) other coins of a similar era in your collection, or if your collection isn't big enough yet, on the sites of reputable dealers such as HJB, Waddell, Spink, CNG and

(c) other coins sold by the same seller.

Questions to ask:

(2.1) is the "style" the same as the catalogue (this is the key determinant which only the eye can tell)

(2.2) is the "strike" similar to coins of that era: does the sharpness of strike look typical, are wear patterns sensible (i.e. high relief more worn looking than low relief), are characteristics such as offstrikes, flan size, strength/weakness typical of the real thing, does it look as if high points or lettering might have been improved by tooling?

(2.3) does the "surface" colour and texture look/feel similar to coins from the same era in your hand. Look for metal flow outwards from the edges of lettering and devices and sharp transitions between devices and field (good: evidence of striking) surface roughness bumps or indentations (not so good, might indicate casting), corrosion (good, at least as regards authenticity) colour uniformity (the less uniform, the less to be suspicious about)

(2.5) are there obvious similarities in style/strike/surface or technique between this coin and other coins of different eras sold by the same seller. If all the seller's coins are the same colour or have the same style of lettering, regardless of era, that's very odd. For example all the Toronto-ring coins look so obviously similar that its clear they came from the same factory.

3. if answers to Q2 raise any significant concerns then classify the coin as "uncertain" unless there's clear red-flags that suggest its a forgery. (2.1) is a key determinant (the style should always match the catalogue) whilst (2.2 2.3 2.4) are indicators, some, but not all, of which should match the coins you are comparing with. (2.5) is a red-flag warning. If one or two symptoms are odd (e.g. surface roughness) there may be perfectly good reasons (e.g. its due to
corrosion, or the dies on these coins weren't polished so its similar to other coins) so think things through carefully before condemning a coin. Remember that most offerings by very-high-feedback sellers are
indeed genuine so if in doubt, ask the seller a question and wait a day for a response BEFORE condemning the coin on an email group.

4. if the coin looks OK after Q2, then you should certainly assume its genuine (and 99% of the time you will be right). Buy it and give it the respect it deserves in your collection.

5. But ... 1% of the time you may buy a forgery that looked and felt perfectly genuine. You'll find out when exact copies (die and wear matches) pop-up at later auctions or when you realise there's a family-resemblance with other coins sold by this dealer. Tough. Try to get your money back, put it down to experience, alert CFDL, and review your coin carefully against my checklist to see if there was indeed warning signs you should have noticed earlier. There are, as we often read on this list, very clever forgers who can make sophisticated copies - however its not easy to make a really good copy that will pass expert scrutiny, so when they do, they're likely to make multiples which will be spotted eventually.

6. As there's not much point in the average collector worrying too much about the really top-end forgeries, put your energy into serious study of the stylistic factors (Q2) that are characteristic of genuine coins. Buy lots of books with good photos. Buy lots of coins from reputable dealers, and look at them carefully and feel them closely (don't buy slabbed coins or you'll never be able to learn about touch and textures!!!). Know your coins inside out and you'll be 99% protected from forgeries.

7. Finally, consider shifting your collecting preference to less sexy series that have less attention from the forgers. Republican or late Roman bronzes will be much safer than high empire sestertii or imperatorial silver; Greek fractions and bronzes safer than fine style tetradrachms. If you insist on collecting Galba Sestertii, Brutus denarii, and Sicilian tetradrachms, then stick to bricks-and-mortar dealers until you really know what you are buying. Better to become an expert in a little known corner, and laugh at the pathetic forgery attempts as they pass you by.